1. Field of the Invention
The present invention relates generally to a method of preparing a variable permeability material for the filling of voids in a subterranean formation and, more specifically, to a method of filling large voids created by open hole completions to permit conversion to cased hole completions or to permit permeable cementing of a perforated casing in a subterranean formation to facilitate secondary or tertiary recovery operations
2. Brief Description of the Prior Art
Numerous wells, particularly in older fields, have been open hole completed in one or more zones over an interval that may extend several hundred feet. Many of such wells have at least two and often three or more sections which, have been shot with explosives. The void area in the open hole surrounding the shot zone often has a diameter which exceeds 20 inches. To effect secondary recovery through waterflooding or carbon dioxide miscible flooding injection treatments, it is necessary to provide zonal isolation to the producing zones to minimize losses of injection water or carbon dioxide to non-productive zones. The zonal isolation can be effected in some situations by cementing casing within the open hole, however, when substantial voids are present in the zone of interest, cement is unsatisfactory. In such a situation, the cement sheath surrounding the casing after filling the shot hole is so thick that it is not possible to perforate the casing and effect communication through the cement to the zone of interest. This necessitates plugging and abandonment of the open hole and the drilling of a new well to effect isolation of the zone of interest. Such plugging and drilling operations substantially increase the cost of the secondary or tertiary hydrocarbon recovery project and in many instances may make the project economically unfeasible.
It would be desirable to provide a method by which void spaces surrounding a conduit penetrating a selected zone of interest in a subterranean formation can be filled with a variable permeability fill material whereby communication can be maintained between said zone of interest and said conduit while isolating said zone of interest from other portions of subterranean formations.